Make compilation work with yersterday's rust version

src/smtp/commands.rs

@@ -139,7 +139,7 @@ impl FromStr for Command {
     }
 }
 
-impl fmt::Show for Command {
+impl fmt::Default for Command {
     /// Format SMTP command display
     fn fmt(s: &Command, f: &mut fmt::Formatter) {
         f.buf.write(match *s {
@@ -213,4 +213,4 @@ mod test {
     fn test_get_argument_command() {
         assert!(SmtpCommand::new(~"EHLO", Some(~"example.example")).get_formatted_command() == format!("EHLO example.example{}", ::common::CRLF));
     }
-}
+}